Pipes are often required to be capped or plugged when the need for the pipe is no longer required. The goal of the capping or plugging is to prevent the contents of the pipe from exiting the pipe and/or to prevent material outside the pipe from entering the pipe. Occasionally, the cap or plug is required to be permanent. As such, the cap or plug should provide a perfect seal. One situation, for example, which may require a permanent cap or plug is when liquid and/or solid hazardous waste is cleaned from storage tanks.
As the tanks are being cleaned, it is desirable to isolate those pipes that may discharge material back into the tanks. Otherwise a portion of a tank that was cleaned may need to be recleaned if additional material is introduced into the tank. Additionally, because hazardous waste that combines with nonhazardous waste typically makes the non-hazardous waste hazardous, preventing the introduction of non-hazardous waste into the tank decreases the total amount of hazardous waste to be cleaned. As such, preventing the introduction of other material into the storage tank is particularly important when cleaning hazardous material from a storage tank.
Although plugging a pipe is a relatively simple operation when the pipe is accessible and is in a clean environment, plugging a pipe in a restricted access environment containing hazardous waste is more complicated. Hazardous waste, and in particular radioactive hazardous waste, can prevent a human being from directly performing the operation. In such a situation, a substitute for a human, for example a robotic arm, is preferably used to perform the operation. However, such a substitute, like a robotic arm, currently lack the dexterity of a human hand. Additionally, the substitute would likely be guided by video camera instead of human sight, and a video camera provides poor depth perception for an operator. As such, equipment to plug a pipe for use by a human will be difficult for an operation in which a human cannot directly perform the operation.
Another problem associated with plugging pipes is that the pipes to be plugged can have different angular orientations. For example, the pipe could be horizontal, vertical, or in a position in between. Thus, depending upon the orientation, different forces act upon the cap and these forces can change how the pipe is plugged and the method of plugging the pipe. For example, with a vertically oriented pipe, unless the cap is fixed upon attachment, the cap must be prevented from falling off the pipe from the force of gravity. Thus an additional piece of equipment may be needed to hold the cap in place until the cap is permanently fixed to the pipe.
Still another problem associated with the plugging of a pipe is that the pipe may not be round and/or clean. For example, depending upon the material flowing through the pipe and the age of the pipe, material may have accumulated within the pipe. The pipe could also be partially corroded. As such, both the exterior and interior of the pipe may not be perfectly clean.
Many reasons also exist for why the pipe may not be perfectly round. For example, wear and tear on the pipe may cause the pipe to go out of round. One particular example is when the pipe is cut to be capped. In such a situation, the cutting of the pipe may cause the pipe to go out of round or create burrs on the pipe. Additionally, the aforementioned accumulations and corrosion may also cause the pipe to go out of round. As such, a pipe that is out of round or a pipe that is not clean may not be efficiently capped using current methods.
One current method of plugging a pipe is to fill the pipe with grout. Before filling, a second plug must be inserted into the pipe to block the flow of grout to all open sections of the pipe. A high pressure pump typically pumps the grout into the pipe. A pipe is then typically filled with approximately 20-30 feet of grout. Several problems are associated with the use of grout in a storage tank containing highly hazardous material in into which only a robot can enter. One such problem is that the grout cannot be easily placed within the pipe because of. limitations inherent with the use of a robotic arm. As previously stated, the robotic arm cannot be manipulated as dexterously as a human hand and this is exacerbated by use of the video camera to guide the movement of the robotic arm. Also, the hose system supplying the grout must be flushed immediately after use to prevent clogging the equipment. However, performing this operation inside the tank will increase the amount of hazardous waste to be cleaned. Additionally, tests have shown that grout does not provide a permanent seal over time when the grout is constantly subjected to water. Thus, not only is the introduction of the grout inside the pipe problematic, the grout will not necessarily provide a permanent seal.
Another tool that can be used to cap a pipe is to use a commercially available pipe plug. However, this tool requires that the pipe be perfectly round and clean before application. Otherwise, the tool will not necessarily plug the pipe. As such, this tool may not be appropriate for pipes that are out of round and/or not clean and cannot be placed into round and/or cleaned because of where the pipe is located. Additionally. this tool is only intended to be used temporarily, and thus would likely not provide a permanent seal.
This tool also requires that a nut be tightened as part of the installation process. Tightening of a nut is a process not easily accomplished by a robotic arm that is not specifically adapted for tightening of a nut. Also, even if the robotic arm is specifically adapted to tightening the nut, this adaptation would hamper the robotic arms ability to deliver the plug into the pipe. As such, two robotic arms would likely be necessary to apply this tool. Another problem associated with this tool is that it must be very precisely aligned within the pipe, and the required alignment is difficult to perform robotically.
Other methods of capping a pipe include welding a cap onto the pipe or applying a threaded cap onto a threaded pipe. Although relatively simple to perform when the pipe can be easily accessed, these methods are very difficult to perform robotically with a video camera. Additionally, if a threaded cap is to be used and the pipe does not have threads, for example after the pipe has been cut, creating the threads on the pipe robotically is also very difficult.
As such, the currently available tools are impracticable with use in a hazardous waste environment, particularly one in which a human being can not directly work. Also, the currently available tools do not permanently and adequately seal pipes that are not clean and are not perfectly round.